A significant portion of the ethylenediamine (EDA) made commercially is by the continuous reaction of monoethanolamine (MEA) and ammonia in the presence of hydrogen over a fixed bed reductive amination catalyst. The reaction unavoidably generates a variety of polyalkylene polyamines as well. Illustrative of many of them are the following:
AEEA-N-(2-aminoethyl)ethanolamine PA0 HEP-N-(2-hydroxyethyl)piperazine PA0 DETA-Diethylenetriamine PA0 AEP-N-(2-aminoethyl)piperazine PA0 TETA-Triethylenetetramine PA0 TEPA-Tetraethylenepentamine PA0 PEHA-Pentaethylenehexamine PA0 NTEA-Nitrilotrisethylamine PA0 TETA-Triethylenetetramine PA0 DiAEP-Diaminoethylpiperazine PA0 PEEDA-Piperazinoethylethylenediamine PA0 AETETA-4-Aminoethyltriethylenetetramine PA0 TEPA-Tetraethylenepentamine PA0 AEPEEDA-Aminoethylpiperazinoethylethylenediamine PA0 PEDETA-Piperazinoethyldiethylenetriamine PA0 "The apparently simple reaction of NH.sub.3 and MEA to yield EDA is deceptive, for several catalytic steps are involved, and a number of side reactions occur."
TETA Isomers:
TEPA Isomers:
Gibson, et al., U.S. Pat. No. 4,400,539, patented Aug. 23, 1983, describes such a process for the manufacture of ethylenediamine. The patent describes a continuous process involving the reductive amination of MEA. A further elaboration of the process of the Gibson, et al. patent is described in Winters, U.S. Pat. No. 4,404,405, patented Sep. 13, 1983. The Gibson, et al. and Winters patents characterize the relative commercial values attributed to ethylenediamine and piperazine. The direction which the art has been moving in recent years has been away from piperazine towards a more favored product, EDA. These patents provide ample descriptions of recovery systems for the separations and recovery of the various products of the reaction.
Another valuable product of the reaction is DETA. The market demand for DETA has been progressively increasing in recent years. It is a desirable co-product with EDA.
The compositions generated by that reaction are dependent upon a number of factors such as the selection of catalyst for carrying out the reaction, the ratio of reactants, the temperature, the pressure, reactant flow velocity through the catalyst zone, the shape and form of the catalyst, the presence and absence of other reactants such as water, and the like considerations. There are a wide variety of reductive amination catalysts for this reaction. Typically, they are viewed as hydrogenation catalysts. The most prevalent of them utilize nickel as an important ingredient. Raney nickel has for years been viewed as a good hydrogenation catalyst. In recent years, nickel in combination with other metals has grown to be a favored catalyst for effecting the reductive amination reaction.
An excellent survey of that process and the alkyleneamines compositions generated thereby can be found in Barnes et al., Ind. Eng. Chem. Prod. Res. Dev. 1981, 20, 399-407. Table II, at page 402, lists a variety of patent examples and the disclosed products of MEA ammonolysis.
According to Barnes et al.
The variety of products generated by that reaction reflects the complexity of the chemistry involved.
Lichtenberger, et al., U.S. Pat. No. 3,068,290, patented Dec. 11, 1962, referred to in Table II of Barnes et al., supra, describes the batch manufacture of EDA by the reaction of MEA and ammonia in the absence of hydrogen in the presence of Raney nickel in an autoclave, and depicts in Example III, the following composition, exclusive of MEA and water:
______________________________________ Product Weight (g.) Moles Mole % ______________________________________ EDA 260 4.48 56 PIP 70 0.81 10 DETA 103 1.0 13 AEEA 138 1.33 17 TETAS + 48 .33 4 VARIOUS AMINES ______________________________________
Because the various amines are unknown compositions, they were treated as TETAS for the purposes of this characterization.
Johansson, et al., U.S. Pat. No. 3,766,184, patented Oct. 16, 1973, criticizes the commercial applicability of the catalyst, and hence the process, of Lichtenberger, et al., see the discussion at col. 2, lines 18 to col. 3, line 5. However, a point not raised by Johansson, et al., is the absence of hydrogen in the process of Lichtenberger, et al. The absence of hydrogen makes the process of Example III of Lichtenberger, et al. not readily reproducible, if ever reproducible, in a continuous process.
It is fairly well appreciated in the reductive amination art that the reductive amination catalyst must be first reduced before effecting the reaction, and then continuously reduced during the course of the reaction in order to keep the catalyst active and functioning. The degree of this reduction will determine the catalyst's productivity and selectivity to products. In the case of Lichtenberger, et al.'s Example III, the Raney nickel had to have been reduced with hydrogen prior to use. It is that level of hydrogenation that will sustain the reaction. As the level of the catalyst's surface becomes depleted of bound hydrogen, the catalyst's activity is reduced and its composition is changed. Eventually the catalyst will become depleted of its bound hydrogen, and when that occurs, the reaction terminates. In the course of the reaction, the composition of the reaction product changes from what it was at the start of the reaction. What is found in the reactor is a composite composition that changes over the course of the limited life of the catalyst. Needless to say that this is not an acceptable parameter of a commercial process.
Cowherd, U.S. Pat. No. 4,568,746, patented Feb. 4, 1986, describes a process for the manufacture of DETA by the selfcondensation of EDA or the coreaction of EDA and MEA. Another product of the reaction is ammonia. Ammonia is not provided in the feed to the reaction. Important process features cited in that patent is the use of a nickel, cobalt or rhodium catalyst, and a temperature between about 170.degree. C. to about 210.degree. C. with an EDA conversion less than about 35%. The only illustrations using MEA employed EDA/MEA mole ratios of 6:1 and 1:1.
As indicated above, there is a significant market demand for DETA. It would be desirable to be able to satisfy that demand from a cost standpoint by modifying slightly the commercial processes directed to the manufacture of EDA from the reaction of MEA and ammonia, to the production of EDA and DETA as major products.
It would be desirable to have continuously produced compositions generated by the reaction of MEA and ammonia over a fixed bed of a reductive amination catalyst under commercial conditions that are rich in EDA and DETA, and that are not disproportionately high in PIP, other cyclics and higher polyalkylene polyamines such as the TETAs, TEPAs and the higher ethoxylates and alkyleneamines thereof.
It would be very beneficial to have a process which increases one's ability to generate the manufacture of desirable products such as EDA and DETA without generating large amounts of cyclic alkylenepolyamine products. In addition, it is also desirable to have a process which emphasizes the manufacture of DETA over a reductive amination catalyst, without the need of avoiding the use of ammonia as exemplified in Cowherd, and thus co-generating the production of EDA. These features are provided by the invention.